Moenkhausia uirapuru, a new species from the upper rio Guapore, Chapada dos Parecis, Mato Grosso, Brazil (Teleostei: Characidae)

Moenkhausia uirapuru, new species, is described from right side tributaries of the upper rio Guapore (rio Madeira basin), Mato Grosso State, Brazil. Based on shared putative synapomorphies of the color pattern in life, the new species seem to be closely related with M. cosmops and the currently non-congeneric Hemigrammus skolioplatus, which are distributed in neighbouring hydrographical systems in the Chapada dos Parecis, a low-lying plateau at the divide of the upper rio Guapore, upper rio Tapajos and upper rio Paraguai basins. These three species, in spite of typologically assignable to the genus Hemigrammus due to the incompleteness of the lateral line, are considered to be putative monophyletic group belonging to the Moenkhausia oligolepis species complex. The complementary distributions presented by M. uirapuru, M. cosmops and H. skolioplatus seems to indicate a complex vicariant scenario where hydrographical reconfigurations due to tectonic activity might have played a major role in the evolution this putatively monophyletic clade. (AU)